Plants such as forsythia, weigela, mock orange, azalea, rhododendron, mountain laurel, andromeda, spirea, viburnums, lilac and spring-flowering roses begin their flower buds in late summer. Before the forming flower buds can bloom in the spring, they must undergo a cold dormancy during fall and winter. As temperatures rise in the spring, the flowers begin to open. Their opening time is governed by day and night temperatures and their species.

Pruning these plants in autumn means fewer flowers come March, April and May.

Fruit trees do require early pruning. To produce larger fruit, apples, peaches, pears and cherries must be pruned before they blossom in the spring. Fall pruning, however, may cause flowers to open earlier than normal, making them more susceptible to late frost damage.

Even more dangerous is the wide-spread practice of mounding mulch around trees and shrubs. From my experiences working with homeowners, I judge that more landscape plants die from over-mulching than any other cause.

Here’s what I mean.

Recently, a customer at the Deale Farmers’ Market complained to me that she had replaced a dogwood tree in her landscape twice. Now the third plant was dying. She irrigated the dogwood correctly, twice weekly with five gallons of water each time. And she planted it on the shallow side as I had instructed her when she replaced the second tree.

I agreed to make a diagnostic visit on my way home. I didn’t even have to get out of my truck to tell what was wrong: over-mulching. I’d estimate she had close to two feet of red mulch piled around the base of the tree.

Over-mulching kills plants by suffocating the roots, which need oxygen. The more mulch you pile over the roots, the less oxygen becomes available in the soil. Without adequate oxygen, roots die, followed by the entire plant. Some plants  among them azaleas, rhododendrons, boxwoods, dogwoods and mountain laurel  have extremely shallow roots because they need lots of oxygen. Load on the mulch, and these roots suffocate.

Instead of mulching and pruning, keep busy this the fall raking leaves or starting a compost pile. Paint your garden tools with iridescent paints to make them easier to find next year. Another mowing and you can winterize your lawnmower, which will make it last longer and start easier next spring. And don’t forget to sharpen your clippers so you’ll be ready for spring prunning.

Ask Dr. Gouin your questions at frgouin@erols.com. All questions will appear in Bay Weekly. Please include your name and address.